Hi
I've found the ellen carney you've mentioned in a tree on ancestry her fusband was John carney and she had a son James aged 12 in 1861, from what i can see she had a son patrick 3 years older than her son ames but ther other children were daughters and so the james in 1891 (her grandson) is from one of the sons, BUT
the same ellen carney and husband john are in another tree on ancestry and there's something abit odd there, the person whose done the tree has the father john married to two women and having two families at the same time, one in liverpool and one in birmingham!! he must have had a bike! Anyway I'm not trusting that one just yet!
there is no sign in the tree of where james snr was in 1881 or 1891 , so i'll have a mooch about and see if he turns up with his son james aged 2-3 in 1881.